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3-Digit Mental Addition and Subtraction Worksheet

Mental maths lesson 20: Add and subtract 3-digit numbers left to right · Set 312 · 40 questions
TalentJR

How to do it in your head (Hundreds first): Keep the first number as it is and split the second into hundreds, tens and ones. Add (or take away) the hundreds first, then the tens. Finish with the ones — bridge through a ten if you need to.

NameDateTime takenScore ___ / 40
  1. 1.454 − 151 =
  2. 2.540 + 225 =
  3. 3.230 + 582 =
  4. 4.789 + 194 =
  5. 5.375 + 571 =
  6. 6.184 + 112 =
  7. 7.923 − 428 =
  8. 8.356 + 512 =
  9. 9.507 − 294 =
  10. 10.744 + 594 =
  11. 11.507 + 341 =
  12. 12.745 + 685 =
  13. 13.212 + 484 =
  14. 14.148 + 164 =
  15. 15.494 + 146 =
  16. 16.477 − 142 =
  17. 17.682 + 211 =
  18. 18.188 + 649 =
  19. 19.771 − 231 =
  20. 20.175 + 483 =
  21. 21.820 − 502 =
  22. 22.504 + 666 =
  23. 23.524 + 156 =
  24. 24.205 + 231 =
  25. 25.722 + 476 =
  26. 26.834 − 574 =
  27. 27.603 + 363 =
  28. 28.416 + 201 =
  29. 29.620 + 217 =
  30. 30.422 + 354 =
  31. 31.535 + 184 =
  32. 32.626 + 175 =
  33. 33.882 − 362 =
  34. 34.825 − 241 =
  35. 35.543 − 287 =
  36. 36.449 − 161 =
  37. 37.757 − 445 =
  38. 38.666 + 356 =
  39. 39.467 + 688 =
  40. 40.477 + 274 =

Answer key

  1. 303
  2. 765
  3. 812
  4. 983
  5. 946
  6. 296
  7. 495
  8. 868
  9. 213
  10. 1338
  11. 848
  12. 1430
  13. 696
  14. 312
  15. 640
  16. 335
  17. 893
  18. 837
  19. 540
  20. 658
  21. 318
  22. 1170
  23. 680
  24. 436
  25. 1198
  26. 260
  27. 966
  28. 617
  29. 837
  30. 776
  31. 719
  32. 801
  33. 520
  34. 584
  35. 256
  36. 288
  37. 312
  38. 1022
  39. 1155
  40. 751

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